(NewsNation) — Weather could put a cramp in holiday travel as millions return home from their Thanksgiving break.

AAA predicted that 54.6 million people will travel at least 50 miles from home in the U.S. this week, with 4.5 million of those flying. Typically, Wednesday and Sunday are the busiest days of the holiday season but experts said that could shift this year as people work remotely in hopes of missing the holiday crowds.

As of Thursday, travelers were reporting fewer complications than expected, with relatively few canceled flights.

For those returning home by car on Sunday, weather could snarl some travel plans.

The National Weather Service urged holiday travelers to heed their warnings about a winter storm that was expected to bring snow to the mountain passes starting Saturday night and could drop snow on the metro areas by Sunday into next week.

“Heavy mountain snow is expected tonight through Sunday night for the Cascades,” the weather service said on Twitter. “If you’re traveling, make sure to check with @wsdot_passes for information on tire requirements.”

The National Weather Service has issued heavy snow warnings for parts of the Cascades and the Northern Rockies and rain is expected in the Southeast, Ohio Valley, Great Lakes and Mid-Atlantic regions.

For Northern New England, that rain could turn to snow Sunday night, causing hazardous driving conditions.

For people traveling by air, things look better. On Sunday morning, airline tracking site Flight Aware was reporting about 50 canceled flights and just over 1,000 delays for travelers within the U.S.